Ultrasound systems have been extensively used in the medical field due to the systems non-invasive and non-destructive nature. Specifically, in the ultrasound system, there is no need to perform any surgical operation procedures. Using the ultrasound system allows a medical professional to see the inside of a target object as a high-resolution video image to facilitate operations. As such, the ultrasound system has become very popular in the medical field.
The ultrasound system transmits ultrasound signals to the target object by using an ultrasound probe. The ultrasound probe has a plurality of transducer elements and can receive ultrasound signals (ultrasound echo signals) reflected from the target object, which then forms an ultrasound image showing the inside of the target object.
To improve the resolution of the ultrasound image, a plurality of array type transducer elements are used. Using a number of the transducer elements prevents the ultrasound signal from being diffused compared to using a single transducer element. As such, the ultrasound signal can be electrically focused to thereby improve sensitivity.
Focusing ultrasound signals includes transmit focusing and receive focusing. In the transmit focusing, the transmit order of the ultrasound signals transmitted from each of the transducer elements is determined by a distance difference between each of the transducer elements and the focusing point. As such, the ultrasound signals transmitted from each of the transducer elements, which contribute to a single transmitting/receiving of the ultrasound signals (i.e., formation of one scan line), are simultaneously added at one focusing point in phase. This causes the amplitude of the transmitting ultrasound signals (i.e., ultrasound beams) to peak. In the receive focusing, each of the ultrasound signals reaching the transducer elements are subject to time-delay. This allows the ultrasound signals reflected from the focusing point to be in phase. Many focusing points are required to improve the resolution of the ultrasound image. Further, to produce one ultrasound image, there must be a repetition of the same signal processing procedures for all the focusing points, which deteriorates the frame rate.
To solve the above-described problem, dynamic receive focusing was used wherein transmit focusing points were fixed and receive focusing points were increased, which allowed the ultrasound signals to be finely focused. In the dynamic receive focusing, the transmit focusing points are fixed so that the resolution of the ultrasound image can be improved. As an alternative measure, there was proposed a method of using all transmit focusing signals of adjacent transmit scan lines to acquire ultrasound data of the transmit scan lines.
Further, to improve the lateral resolution of the ultrasound image and the signal-to-noise ratio (SNR), it is ideal to direct the received signal obtained from all transducer elements (channels) contributed to a single reception of the ultrasound signals to a beam former. This implements synthetic aperture imaging (SAI) at a full frame rate, wherein the received signal constitutes more proper radio frequency (RF) data obtained from the received signal. To achieve this, however, it is necessary to simultaneously form low resolution images (LRIs) corresponding to all scan lines and update high resolution images (HRIs), which are already formed by using each of the LRIs. To do this, the received signals must be corresponded at all transducer elements, which are contributed to the single reception of the ultrasound signals, to each of the scan lines, thereby significantly increasing hardware complexity.